Let’s talk about Invisalign Mandibular Advancement!
This week we have had more publicity about Invisalign Mandibular Advancement. So let’s have a look at it.
As I have said before Invisalign has been a significant development in orthodontic treatment. I am, therefore, very interested in their expansion into the teen market. One innovation that looks interesting is their Mandibular Advancement Appliance.
This is the addition of ramps in the molar region of aligners. These are similar to the blocks in the Twin Block appliance. The amount of mandibular advancement is approximately 2mm per set of aligners, resulting in sequential advancement. At this point, it is relevant to mention that investigators have done several trials on sequential advancement with Twin Blocks and these have shown that there are limited advantages in introducing this step.
A panel of Invisalign providers has tested this appliance, and the FDA has approved it. The definition of this is not too clear, but it means the following:
“The U.S. Food and Drug Administration’s approval process provides consumers with assurance that, once it reaches the market place, a medical device is safe and effective in its intended use”.
Importantly, this does not mean that it “works”. We need to remember that AcceleDent was FDA approved and look what happened there!
As a result, we need to be asking questions about its effectiveness. I had a look for case reports, retrospective and cohort studies and I found very little. Although, I understand that there are some case reports on the Invisalign Dr website. However, I found this case report of a patient who had a Class II problem, but this looked like a very mild or even Class I case to me? In the write up they claim an advancement of the mandible.
Here is a video of the appliance working on a cartoon.
This now brings me to the claims that Invisalign makes in their advertising material. I have looked at the glossy brochure and marketing section of their website. This includes statements by several of their well-paid Key Opinion Leaders.
What are the claims?
These are from the FAQ section of the website.
“Give your patients a better Class II treatment experience. Invisalign treatment with mandibular advancement is a clinically proven, more efficient, more patient-friendly choice.*
- Save the cost and time of fitting and repairs
- Treat patients more efficiently
- Increase patient comfort during treatment
- Treat patients in late-mixed dentition
- Correct deep bite in growing Class II patients”.
“This new offering combines the benefits of the most advanced clear aligner system in the world with features for moving the lower jaw forward while simultaneously aligning the teeth. Invisalign treatment with mandibular advancement offers a simpler, more efficient and patient-friendly treatment option than functional appliances to treat teen Class II patients”.
“a multicenter prospective IRB clinical study was completed with 80 patients in North America. Preliminary results from 42 cases thus far show statistically significant correction of Class II malocclusion in growing teen patients”. I have no idea what this means…
What do I think?
I looked closely at the evidence that they quoted on the website about the first claim. The only “proof” that I could find was in the tiny print at the bottom of the page. They got this data from a survey of 8 of the nine orthodontists who took part in the clinical study. They asked them questions on chairside time and whether they thought that the appliance was “patient friendly”.
There was no evidence to support the statement that this was better than other Class II correctors.
Furthermore, I would be amazed to find that this appliance causes mandibular growth (moving the lower jaw forwards) as we know that no functional appliance can do this.
I am wondering at what level of evidence the company and the KOLs are working. This is far from convincing.
In an ideal world, companies or inventors should test their innovations in a clinical trial. However, there are many cases when this is not possible or necessary. For example, when Bill Clark invented the Twin Block, the initial evidence level was case reports. It was trialled several years later after many operators adopted it as a method of treatment.
There was nothing wrong with this approach because extreme claims were not made for its effectiveness and it was freely available as part of the orthodontic armamentarium. Bill Clarke did not charge a fee for every Twin Block that was made.
However, this is different. They are claiming that the new Invisalign appliance is better than other Class II correctors. They are also suggesting that it grows jaws. This is what I have a problem with. These claims are potentially misleading and are similar to those made for other recent developments in orthodontics. Perhaps this is a sign of the times, but there should be a time when we say no, we do not believe you. I wonder if this is long overdue.
Emeritus Professor of Orthodontics, University of Manchester, UK.